As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2010 and are well known to the person skilled in the art.
For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated. The term “up to” and “up to about”, as employed herein, explicitly includes, but is not limited to, the possibility of zero weight-percent of the particular alloying component to which it refers. For example, up to about 0.1% Zn may include an alloy having no Zn.
Heat exchangers and other similar equipment, such as condensers, evaporators and the like for use in car coolers, air conditioning systems, industrial cooling systems, etc. usually comprise a number of heat exchange tubes arranged in parallel between two headers, each tube joined at either end to one of the headers. Corrugated fins are disposed in an airflow clearance between adjacent heat exchange tubes and are brazed to the respective tubes.
The tubes or refrigerant tubes are being manufactured for example by folding a brazing sheet clad on the outside with a brazing material layer.
Alternatively the tubes are produced by means of extrusion. Typical extrusion based heat exchangers come essentially in two designs. The first design uses round tubing and fins that are mechanically attached to the round tubes by first lacing the tubes into holes punched in the fins, and then expanding the tubes to ensure that the tube's outer surface is in close mechanical contact with the fins.
The second typical design uses flat tubing or tubes having a plurality of channels in the tubing, commonly referred to as multi-void tubing or micro multi-void tubing or or multi port extruded tubes or multi-cavity tubing or multi-porthole tubing. This type of heat exchanger tubing is attached to the fins using a brazing process. The cross section of the flow channels can vary, e.g. circular, oval, square, rectangular, or other regular or irregular shapes. Typically, micro multi-void and multi-void tubing are about 10-80 mm in width and about 1-5 mm in height.
For the extruded multi-void tubing a wide variety of aluminium alloys are employed. The AA1000-series aluminium alloys are often selected where corrosion resistance is needed. Where higher strengths are required, the AA3000 and AA6000-series are often used. There are various disclosures of aluminium alloys for use in micro multi-void and multi-void tubing and whereby the alloy composition has been optimised to meet specific improvements in corrosion resistance or strength levels. Examples can be found in each of the patent document publications EP-1564307-A1, EP-1721988-A1, and EP-1892308-A1, and incorporated herein by reference.
Another example is disclosed in US published patent application no 2007/0017605-A1 disclosing a specific Al—Mn—Si aluminium alloy extruded product having improved surface properties. After applying a fluoride-type flux to the surface of a multi-port tube made from the aluminium alloy, the multi-port tube and other members such as a fin material are assembled into a specific structure and joined by brazing in a heating furnace containing inert gas.
There is room for improvement in the art of aluminium extruded alloy tube stock for brazed heat exchangers and for methods of manufacturing such brazed heat exchangers, in particular for brazing methods that do not require the application of a brazing flux material.